Filter device

ABSTRACT

A filter device having at least one filter element ( 37 ) that can be accommodated in a filter housing, and is fluid-connected to a fluid tank ( 1 ) and that has at least one connection appliance ( 29 ) for forming a fluid connection to the filter element ( 37 ), is characterized in that the filter housing is formed by a filter bowl ( 13 ) that is moulded into the tank ( 1 ), at the bowl bottom ( 17 ) of which is situated the connection appliance ( 29 ) associated with the element receiver.

The invention relates to a filter device having at least one filter element that can be accommodated in a filter housing which is fluid-connected to a fluid tank and that has at least one connection unit for forming a fluid connection to the filter element.

Filter devices of this type are readily available on the market in a plurality of constructions and versions. Such filter devices are used mainly to filter fouling in fluids such as hydraulic oil out of the latter. Fouling of the hydraulic oil occurs in the installation or in the start-up of the respective hydraulic system. In addition to this initial fouling, fouling can occur during operation, for example, by penetration of dirt at the hydraulic tank as a result of inadequate tank ventilation, pipe penetrations, piston rod seals, and the like. Fouling can occur within the fluid stored in the hydraulic tank especially in the hydraulic systems of heavy machinery such as earth moving machines, excavators, or the like. Furthermore, in these types of applications of the filter device, it can be useful to effect filtration directly in the region of the hydraulic tank, for example, by installing the filter device directly in the tank.

Under conditions of use as prevail in operation of the filter device in construction machinery or other machinery which is to be operated in the open, due to the higher fouling rates which arise, frequent changing of the filter element must be done. In the course of handling the used, i.e., fouled, filter elements, in these known solutions, there is the risk that contamination both of the system, i.e., especially of the filter housing and the tank, and also of the environment will occur.

DE 10 2006 011 844 B4 discloses a filter element with a filter bowl which borders an interior, with a bottom part which has a flow passage, with a filter medium located in the interior of the filter bowl, and with a valve body of a valve apparatus, which body can be actuated by the fluid pressure, on the fluid passage of the bottom part, the valve body having a screen-like, flexible closing jacket which in the opened-up state blocks the fluid passage and is moved by the fluid pressure in the direction to its closed position, and clears the fluid passage, with the closing jacket in its central region being fixed on a carrier within the filter element and the ring body of the bottom part making a ring edge which forms the valve seat sealing surface and which projects to the inside.

DE 10 2005 001 828 A1 discloses a generic filter device, especially a fitting for forming a fluid-carrying connection to a plastic container, preferably in the form of a tank for accommodating a fluid, specifically a hydraulic fluid, with the fitting having a connection part in the form of a hollow body with a jacket which extends along one longitudinal axis of the hollow body between its ends, with the hollow body being embedded in the plastic of the wall of the container such that one open end of the hollow body on the edge of an opening of the container and at least one partial region of the jacket of the hollow body are surrounded by the plastic of the wall of the container.

The hollow body, which is preferably produced from a metallic material, enables not only the reliable connection to connection parts or attachment parts which form a component of the pertinent hydraulic system, but also contributes concomitantly to reinforcing that region of the plastic container or tank which is located in the region of the opening.

With regard to the possibilities of comparatively simple forming, of low weight and of corrosion resistance relating to the plastic tank, the known solution, however, leaves much to be desired. The known solution is also relatively complex with respect to the host of components to be used and is therefore costly in production.

Based on this prior art, the object of the invention is to provide a filter device of the indicated type which enables a reliable, long-term, leak-free port connection on an opening of a plastic container or plastic tank which helps avoid the aforementioned disadvantages. This object is achieved by a filter device having the features specified in claim 1 in its entirety.

According to the characterizing part of claim 1, one important particular of the invention consists in that the filter housing is formed by a filter bowl which is molded into the tank and on whose bottom the connection unit which belongs to the element receiver is located. In this way, the filter element can be directly inserted into the filter bowl of the filter tank without additional insertion bodies, metallic hollow bodies, or the like; this can be done relatively easily from production, with at the same time a high sealing action in the region of the insertion site into the tank being achieved, in addition to corresponding weight reduction since the number of components to be used can be reduced accordingly. Especially advantageously, this eliminates a filter housing which is to be installed in the tank because the filter bowl itself as an integral component of the tank forms the filter housing.

In especially advantageous exemplary embodiments, on the bottom of the filter bowl a connecting piece is molded which forms a passage for the connection fitting, which is joined to a bottom-side wall section of the tank and through which the connection fitting extends from the outside of the tank into the filter bowl.

Especially advantageously, the arrangement here can be made such that the wall section of the tank adjoining the connecting piece is located in a local indentation which extends upward from the base of the tank. This makes it possible to “countersink” the bottom-side connection completely into the bottom of the tank, as a result of which advantages arise for the installation of the tank in heavy machinery with little available installation space.

Preferably, the connection fitting in the connecting piece is fixed by a screw union that can be a standard screw-in design.

The tank together with the filter bowl which forms an integral component of it can be especially advantageously molded out of plastic.

Furthermore, the filter bowl which is open on the top of the tank can be advantageously closed by a plastic cover which can be screwed to an internal thread located on the edge region of the filter bowl such that the cover with its outside forms a part of the upper tank wall. In these exemplary embodiments, the tank can be configured such that, in a fluid connection proceeding from the tank bottom, the tank with one wall part forms an outer skin part of the pertinent machinery, and only the cover of the filter bowl on the outer skin is visible of the entire filter device.

Furthermore, it is preferably provided that the connection unit for the supply of the fluid to be cleaned leads to the dirty side of the filter element and is a component of the element receiver with which the filter element, which is in the operating position, interacts, with the filter element having a valve arrangement which normally closes the inlet to its dirty side and which can be opened when the filter element is attached to the element receiver. This eliminates the risk that when the filter element is being replaced, fouling which has become attached and/or which has been deposited on the used filter element on the dirty side, when the used filter element is withdrawn from the element receiver, can fall off the filter element and can travel to the clean side. In conjunction with changing the filter element, therefore, no subsequent operations need be carried out to clean the filter housing.

In especially advantageous exemplary embodiments, the filter housing is formed by a filter bowl which is molded into the tank and on whose bottom the connection unit which belongs to the element receiver is located. Especially advantageously, this eliminates a filter housing which is to be installed in the tank because the filter bowl itself as an integral component of the tank forms the filter housing.

The arrangement in this case is especially advantageously such that the filter element through which flow can take place from its inner filter cavity to the outside of its filter medium during filtration is provided with at least one end cap, with this end cap, which is the lower one in the operating position, for the interaction with the element receiver having an inlet fitting which projects into the filter cavity, to which the valve arrangement is attached and which in the operating position engages a connection fitting of the connection unit as a component of the element receiver with sealing.

To form the valve arrangement, the end of the inlet fitting can be spanned by a cap of elastomer material which is provided with notches such that the connection fitting of the connection unit, which fitting penetrates the inlet fitting in the operating position, opens the notches of the cap to form flow slots by mechanical action on the cap. This construction of the valve arrangement can be easily produced especially economically so that the presence of the valve arrangement on the filter element increases its production costs only slightly.

Alternatively, the valve arrangement on the inlet fitting can have a movable valve body which is pretensioned by mechanical closing force into the closed position which blocks the inlet fitting, and when the filter element is attached to the element receiver, it can be moved out of the closed position by the mechanical action of the connection fitting against the closing force. Advantageously, in this valve design, likewise as in the use of an elastomer valve cap, no mechanical effort on the part of the connection unit is necessary for valve actuation, because in both cases the valve opening takes place by mechanical action by means of the connection fitting of the connection unit which in the operating position of the filter element penetrates its inlet fitting.

The invention is detailed below using exemplary embodiments shown in the drawings.

FIG. 1 shows a broken-away part of a fluid tank cut with a vertical cutting plane with the pertinent filter device according to one exemplary embodiment of the invention and

FIG. 2 shows a representation corresponding to FIG. 1 with a second exemplary embodiment of the filter device.

The drawings of the fluid tank 1, which is designed to accommodate a supply of hydraulic fluid, show only an upper wall section 3 and a lower wall section 5, which, together with other wall parts which are not shown, delineate an interior 7 for hydraulic fluid whose level is indicated at 9. The tank 1 is a component of a hydraulic system of a heavy machine, for example, in the form of a small excavator, of the hydraulic system only one tank return line 11 being shown via which hydraulic fluid which is to be cleaned is supplied to the filter device and after completed cleaning is returned from it back to the interior 7 of the tank 1.

The tank 1 is made out of plastic material which is compatible with hydraulic fluid in a rotary molding method, with a filter bowl 13 being molded integrally to the tank walls by rotation inward. The bowl 13, which is open on the top 15 of the tank, extends vertically from the top 15 of the tank into the vicinity of the base of the tank 1, relative to the installation position of the tank 1. The bowl bottom 17 has a centrally located connection opening 19 and outflow openings 21 which are located laterally from the latter via which cleaned fluid travels out of the filter bowl 13 into the interior 7 of the tank 1. The connection opening 19 on the bowl bottom 17 is connected to a connecting piece 23 via which the bowl bottom 17 is connected to the lower wall section 5 of the tank 1. As the drawings show, a port connection 27 of the return line 11 on the filter device is placed within an indentation 25 which is arched upward from the base of the tank 1 so that the connection fitting is, as it were, “countersunk” within the tank bottom.

From the port connection 27 of the return line 11, a connection fitting 29 extends in the form of a cylindrical hollow body which is stepped on its outside through the connecting piece 23 and the bottom opening 19 of the bowl 13 into its interior, the end 31 of the connection fitting 29 being located at a distance from the bowl bottom 17. The connection fitting 29 is fixed in the connecting piece 23 by a threaded insert 33 and forms a component of an element receiver which interacts with the lower end cap 35 of a filter element 37 in order to fix the latter within the filter bowl 13 in its operating position, the filter bowl 13 acting as a filter housing.

The filter element 37, which is shown in its operating position in the drawings, on its lower end cap 35 which conventionally forms an enclosure for a filter medium 39 which in the form of a hollow cylinder surrounds an inner filter cavity 41, has a central inlet fitting 43 which can be slipped onto the connection fitting 29 in the operating position, a sealing element 45 on the inlet fitting 43 sealing relative to the connection fitting 29. The element receiver completes a spacer ring 47 of elastomer material which surrounds the inlet fitting 43 and defines the axial positioning between the end cap 35 and the bowl bottom 17.

The filter bowl 13, which is open on the top 15 of the tank, can be closed by a plastic cover 49 which can be screwed to an internal thread 51 which is located on the edge region of the filter bowl 13 so that the cover 49 is visible only with its outside on the top 15 of the tank. A bypass valve arrangement 55, which is located between the cover 49 and the upper end cap 53 of the filter element 37 with a correspondingly prevailing differential pressure, conventionally clears a fluid connection between the inner filter cavity 41 and the outside of the filter element 37, with the closing spring 57 keeping the bypass valve 55 in the closed, normal operating position.

During filtration, the hydraulic fluid which is flowing into the filter cavity 41 via the connection fitting 29 flows through the filter medium 39 from the inside to the outside so that the cleaned fluid from the space of the filter bowl 13 which surrounds the filter medium 39 and which forms the clean side 59 flows back into the interior 7 of the tank 1 via the outflow openings 21. In the exemplary embodiment from FIG. 1, on the free end region of the inlet fitting 43 which projects into the filter cavity 41, there is a valve arrangement which is formed from a valve cap 61 of elastomer material which traverses the end of the inlet fitting 43. This cap 61 has several notches 63. Without mechanical action applied to the valve cap 61, the valve cap 61 with the notches 63 closed forms a closure of the inlet fitting 43. If, however, the filter element 37, as is shown in FIG. 1, is moved into the operating position and is slipped onto the connection fitting 29 with the inlet fitting 43, the valve cap 61 is opened up by mechanical action of the free end 31 of the connection fitting 29 in the manner shown in FIG. 1, as a result of which the notches 63 are widened into flow slots, so that fluid flows into the filter cavity 41 through the connection fitting 29 for the filtration process. But if the filter element 37 is withdrawn from the connection fitting 29 for element replacement, the valve cap 61 returns into the unwidened position in which the cap 61 with the notches 63 closed closes the end of the inlet fitting 43. This prevents fouling which is located in the filter cavity 41, i.e., the dirty side, from falling out of the filter element 37, and fouling the clean side when the filter element is being replaced. In the handling of the used filter element 37 which has been removed from the filter bowl 13, this reduces the risk of fouling of the environment.

The exemplary embodiment shown in FIG. 2 differs from the first exemplary embodiment only by the construction of the valve arrangement on the inlet fitting 43 of the end cap 35. In this exemplary embodiment, the inlet fitting 43 is extended into the interior of the filter cavity 41, so that the free end 65 of the inlet fitting 43 is located above the end 31 of the connection fitting 29. With its free end 65, the inlet fitting 43 forms a valve seat for a disk-like valve body 67 of the valve arrangement. In the operating position shown in FIG. 2, the axially movable valve body 67 is raised off the end of the inlet fitting 43 against the action of a closing spring 69 because the connection fitting 29 with its inner end 31 has moved a spring carrier 71 upward which is movably guided within the inlet fitting 43, as a result of which the valve body 67 is moved up and raised off the valve seat, the closing spring 69 being more strongly compressed between the spring carrier 71 and a second spring carrier 73 which is located stationary in the inlet fitting 43. If at this point the filter element 37 is pulled off the element receiver and removed from the filter bowl 13 when the element is being changed, when the closing spring 69 is only partially released the valve body 67 moves onto the valve seat on the end 65 of the inlet fitting 43 and closes the latter. Thus, the second exemplary embodiment works in exactly the same way as in the example described first. Since, except for the different design of the valve arrangement, in the two exemplary embodiments, the other components are comparable, not all details which are made the same in the two exemplary embodiments are numbered in FIG. 2. 

1. A filter device having at least one filter element (37) that can be accommodated in a filter housing which is fluid-connected to a fluid tank (1) and that has at least one connection unit (29) for forming a fluid connection to the filter element (37), characterized in that the filter housing is formed by a filter bowl (13) which is molded into the tank (1) and on whose bottom (17) the connection unit (29) which belongs to the element receiver is located.
 2. The filter device according to claim 1, characterized in that on the bottom (17) of the filter bowl (13) a connection piece (23) is molded which is joined to a bottom-side wall section (5) of the tank (1), which forms a passage for the connection fitting (29), and through which the connection fitting (29) extends from the outside of the tank into the filter bowl (13).
 3. The filter device according to one claim 1, characterized in that the wall section (5) of the tank (1) adjoining the connecting piece (23) is located in a local indentation (25) which extends upward from the base of the tank (1).
 4. The filter device according to claim 1, characterized in that the connection fitting (29) in the connecting piece (23) is fixed by a screw union (33).
 5. The filter device according to claim 1, characterized in that the tank (1) together with the filter bowl (13) which forms an integral component of it is molded out of plastic.
 6. The filter device according to claim 1, characterized in that the filter bowl (13) which is open on the top (15) of the tank can be closed by a plastic cover (49) which can be screwed to an internal thread (51) located on the opening edge region of the filter bowl (13) such that the cover (49) with its outside forms a part of the upper tank wall.
 7. The filter device according to claim 1, characterized in that the connection unit (29) is intended for the supply of the fluid to be cleaned to the dirty side (41) of the filter element (37) and is a component of the element receiver with which the filter element (37) which is in the operating position interacts, and that the filter element (37) has a valve arrangement (61; 67, 69) which normally closes the inlet to its dirty side (41) and which can be opened when the filter element (37) is attached to the element receiver.
 8. The filter device according to claim 1, characterized in that a filter element (37) through which flow can take place from its inner filter cavity (41) to the outside of its filter medium (39) during filtration is provided with at least one end cap (35) and that this end cap (35) which is the lower one in the operating position for the interaction with the element receiver has an inlet fitting (43) which projects into the filter cavity (41), to which the valve arrangement (61; 67, 69) is attached and which in the operating position engages a connection fitting (29) of the connection unit as a component of the element receiver with sealing (45).
 9. The filter device according to claim 1, characterized in that to form the valve arrangement the inner end of the inlet fitting (43) is spanned by a cap (61) of elastomer material which is provided with notches (63) such that the connection fitting (29) of the connection unit, which fitting penetrates the inlet fitting (43) in the operating position, by mechanical action on the cap (61) opens its notches (63) to form flow slots.
 10. The filter device according to claim 1, characterized in that the valve arrangement on the inlet fitting (43) has a movable valve body (67) which is pretensioned by mechanical closing force (69) into the closed position which blocks the inlet fitting (43) and, when the filter element (37) is attached to the element receiver, it can be moved out of the closed position by the mechanical action of the connection fitting (29) against the closing force (69). 